The present invention relates to an arrangement which enables a part which is attached to a support frame to be held pressed against a rotatable member which is mounted within that support frame. This arrangement is applicable particularly, but not exclusively, to apparatus which is used to record data on a magnetic recording medium, and to impactless magnetic printing machines.
Data recording apparatus and printing machines of this kind generally have a recording medium which is formed by a carrier coated with a layer of magnetic material, which carrier may take various forms, being for example in the form of a drum, a flexible tape or a disc. Data is recorded on this recording medium by means of at least one magnetic recording head adjacent to the moving recording medium. To insure that the recording medium is properly magnetized and to avoid, in particular, the undesirable effects caused by stray magnetic flux from the head, it is essential for the distance which separates the head from the recording medium to remain constant and less than a predetermined limiting value which, in present-day applications, has been found to be equal to a few microns. Setting the head and the recording medium to maintain this distance as constant as possible has always proved a difficult problem to solve, and this has resulted in practice in the head being placed in contact with the recording medium.
Thus, in known recording apparatus such for example as that which is described and illustrated in French Patent Specification No. 1,322,983, the recording medium is formed by a flexible magnetic card which is held against the recording head while being moved past the head by pneumatic suction. This solution, which is perfectly suitable in cases where the recording medium is relatively flexible, is not suitable when the recording medium is rigid and indeformable, as it is, for example, when it is formed by a drum. In the case of a drum it is in fact virtually impossible to obtain perfect contact between the recording head and the drum, by reason of the fact that the drum, despite all the care taken in its manufacture, often has structural defects such as eccentricities or surface irregularities which, even though small, prevent all the points of the sliding surface of the head from being in simultaneous contact with the drum.
This disadvantage is even more noticeable when the recording apparatus or the printing machine has a plurality of recording heads which are arranged one beside the other along a generatrix of the drum and which are combined into a single assembly. When this is the case it is in fact no longer possible to obtain perfect contact between all of the heads and the surface of the drum. This disadvantage could be overcome by mounting each head separately on a resilient support in such a way as to enable the head to be forced against the surface of the drum, but with this solution it would not be possible to prevent the heads from performing relatively large translatory movements in relation to the fixed parts of the machine both in the direction of movement of the drum and in a direction parallel to the axis of rotation of the drum. Consequently, this solution would be incompatible with the need for precise positioning of the items of data recorded on the drum.